N4H7T: Installation Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
8
Defrost
The defrost control is a time/temperature control which has field
selectable settings of 30, 60, 90, or 120 minutes, factory set to 60
minutes. These settings represent the initial time period that must pass
after closure of the defrost thermostat before the defrost sequence
begins, after which the defrost period varies with defrost length. If Quiet
Shift 2 is enabled, the variable defrost intervals will be disabled to
provide options where using a specific setting is desired. In this case the
30, 60, 90, or 120 minutes setting will not change unless the dipswitch is
changed and power is cycled.
The defrost thermostat senses coil temperature throughout the heating
cycle. When the coil temperature reaches the defrost thermostat setting
of approximately 32°F (0°C), it will close, which energizes the DFT
terminal and begins the defrost timing sequence. When the DFT has
been energized for the selected time, the defrost cycle begins. Defrost
cycle is terminated when defrost thermostat opens, or automatically after
10 minutes.
Defrost Speedup
To initiate a forced defrost, speedup pins (J1) must be shorted with a flat
head screwdriver for 5 seconds and RELEASED. If the defrost
thermostat is open, a short defrost cycle will be observed (actual length
depends on Quiet Shift- 2 switch position). When Quiet Shift- 2 is off,
only a short 30 second defrost cycle is observed. With Quiet Shift- 2 ON,
the speedup sequence is approximately 3 minutes; 1 minute compressor
off period followed by 30 seconds of defrost with compressor operation.
When returning to heating mode, the compressor will turn off for an
additional 1 minute.
If the defrost thermostat is closed, a complete defrost cycle is initiated. If
the Quiet Shift- 2 switch is turned on, the compressor will be turned off
for two 1 minute intervals as explained previously.
A05378
Fig. 11 – Defrost Control
Check Charge
NOTE:
CHARGE IN HIGH STAGE ONLY.
Factory charge amount and desired subcooling are shown on unit rating
plate. Charging method is shown on information plate inside unit. To
properly check or adjust charge, conditions must be favorable for
subcooling charging. Favorable conditions exist when the outdoor
temperature is between 70°F and 100°F (21.11°C and 37.78°C), and the
indoor temperature is between 70°F and 80°F (21.11°C and 26.67°C).
Follow the procedure below:
Unit is factory charged for 15ft (4.57 m) of lineset. Adjust charge by
adding or removing 0.6 oz/ft (.018 kg/m) of 3/8 liquid line above or
below 15ft (4.57 m) respectively.
For standard refrigerant line lengths (80 ft/24.38 m or less), allow system
to operate in cooling mode at least 15 minutes. If conditions are
favorable, check system charge by subcooling method. If any adjustment
is necessary, adjust charge slowly and allow system to operate for 15
minutes to stabilize before declaring a properly charged system.
If the indoor temperature is above 80°F (26.67°C), and the outdoor
temperature is in the favorable range, adjust system charge by weight
based on line length and allow the indoor temperature to drop to 80°F
(26.67°C) before attempting to check system charge by subcooling
method as described above.
If the indoor temperature is below 70°F (21.11°C), or the outdoor
temperature is not in the favorable range, adjust charge for line set length
above or below 15ft (4.57 m) only. Charge level should then be
appropriate for the system to achieve rated capacity. The charge level
could then be checked at another time when the both indoor and outdoor
temperatures are in a more favorable range.
NOTE:
If line length is beyond 80 ft (24.38 m) or greater than 20 ft
(6.10 m) vertical separation, See Long Line Guideline for special
charging requirements.
Heating Check Chart Procedure
To check system operation during heating cycle, refer to the Heating
Check Chart on outdoor unit. This chart indicates whether a correct
relationship exists between system operating pressure and air
temperature entering indoor and outdoor units. If pressure and
temperature do not match on chart, system refrigerant charge may not be
correct. Do not use chart to adjust refrigerant charge.
Verify units for proper switching between low & high
stages
Check the suction pressures at the service valves. Suction pressure
should be reduced by 3-10% when switching from low to high capacity.
Compressor current should increase 20-45% when switching from low
to high stage. The compressor solenoid when energized in high stage,
should measure 24vac at leads inside control box.
When the compressor is operating in low stage the 24v DC compressor
solenoid coil is de-energized. When the compressor is operating in high
stage, the 24v DC solenoid coil is energized. The solenoid plug harness
that is connected to the compressor HAS an internal rectifier that
converts the 24v AC signal to 24v DC.
DO NOT INSTALL A PLUG
WITHOUT AN INTERNAL RECTIFIER
.
